Trade-offs between production and tree biodiversity in coffee agroforests of Guinea and their contribution to landscape resilience and farmers livelihood
Résumé
Coffee
agroforests are typical of the multi-strata cropping systems for which there is
a growing interest as a pathway towards sustainable agriculture. Due to their
pluri-specificity, they provide interesting trade-offs between services and
productions that participate to resilience of tropical landscapes and of
farmers livelihoods. There is however still little knowledge about the
trade-offs between coffee yield (one of the components of production) and tree
biodiversity (one of the component of ecosystems services) on the basis of
field observations. Our study aims to assess these trade-offs on coffee
agroforest plots in the region of Guinée Forestière (Guinea). We sampled 27
coffee agroforest plots clustered into three shade levels over the coffee
stand. On each plot, we characterized (i) canopy structure, (ii) tree
biodiversity (iii) coffee yield and (iv) farmers’ practices. Data were also
collected on forest stands as well as monocrop coffee stands to be used as
reference of tree biodiversity and coffee production respectively. Coffee plant
density was around 1030 (±330) ha-1 without significant difference between the
shade levels groups. Tree biodiversity of mature trees and tree seedling was
significantly higher in forest than in agroforest plots. Within agroforest
plots, diversity of mature trees was higher in high shade plots than in low
shaded plots, whereas tree seedling diversity was similar among the shade
levels. Coffee yield decreased when shade cover increased on coffee stands (r²:
0.36), with significant differences of yield per coffee plant and per ha
between the high shade (129 ± 161 kg. ha-1.year-1) and low shade plots (1002 ±
735 kg. ha-1.year-1). The level of intensification of farmers’ practices was
not correlated with coffee yield and tree biodiversity. Despite a high
variability within a shade level group, coffee yield and mature tree
biodiversity were significantly correlated and their relationship followed a
concave form. Using natural forest as a reference for tree biodiversity and
monocrop coffee fields as a reference for yield, discuss the tradeoffs between
economic return from production and biodiversity conservation and how cropping
system structure and management could help to shift the relationships towards a
convex curve. Among medium shade coffee agroforest plots, some fields suggest a
significant leeway to design agroforest structure and to manage their input in
order to combine, in a profitable way, the production of coffee berry and
ecosystems services mediated through tree diversity. Including the products
from other plants during the lifetime of the agroforest provides additional
leeway in the search for the best trade-offs between farmers’ livelihoods and
landscape resilience.
Mots clés
Africa
coffee canephora
farmers’practices
food security
farmers livelihoods
profitability
shade
structure of vegetation
yield
tree diversity
Agroforêt
café
systèmes de culture
agriculture durable
paysages tropicaux
agriculteurs
biodiversité
arbres
services écosystémiques
Guinée Forestière
rendements
ombre
monoculture